The disclosed embodiments relate to a medical device. Specifically, the disclosed embodiments relate to a balloon catheter inserted into a narrow part formed in a blood vessel such that the catheter enlarges the narrow part to obtain a blood flow.
Conventionally, balloon catheters are known as therapeutic catheters that are inserted into constrictions formed in blood vessels and are enlarged therein. A balloon catheter mainly includes a balloon acting as an inflating body, an outer shaft adhered to the proximal end of the balloon, and an inner shaft inserted into the balloon and the outer shaft. The inner shaft is used for inserting a guide wire. An inflation lumen provided between the outer shaft and the inner shaft is used for passing a liquid (e.g., a contrast medium and a physiological saline) for inflating the balloon.
Known balloon catheters include an over-the-wire balloon catheter (OTW balloon catheter) having an inner shaft extending from the proximal end to the distal end to insert a guide wire, and a rapid-exchange balloon catheter (RX balloon catheter) having a guide wire port for inserting a guide wire around an intermediate part between the proximal end and the distal end and an inner shaft extending from the guide wire port to the distal end.
An RX balloon catheter features a guide wire that can be more easily replaced with another than that of an OTW balloon catheter, but the catheter has low stiffness and low pushability in a blood vessel because the guide wire is not inserted to the proximal end behind the guide wire port. In order to solve the problem, in an RX balloon catheter, a metallic reinforcing member is generally provided from the proximal end to the vicinity of the guide wire port in an inflation lumen provided between an outer shaft and an inner shaft, thereby achieving higher pushability (For example, see U.S. Pat. No. 5,389,087 and Japanese Patent Laid-Open No. 2013-106798).
In balloon catheters described above, however, the distal end of a reinforcing member is fixed to only one of the inner surface of an outer shaft and the outer surface of an inner shaft. Thus, when an operator pushes the balloon catheter to the end of the catheter, a pushing force is transmitted to only one of the outer shaft and the inner shaft through the distal end of the reinforcing member, which may displace the outer shaft and the inner shaft relative to each other. This causes the balloon catheter to have low pushability. Further, when the operator pushes the balloon catheter forward so as to insert the balloon catheter into a narrow part in a blood vessel, the distal end of the reinforcing member may detach from the inner surface of the outer shaft or the outer surface of the inner shaft, preventing transmission of a pushing force to the outer shaft or the inner shaft.